[in the SPOTLIGHT]
Richard J. Davidson
and Antoine Lutz
Buddha’s Brain:
Neuroplasticity and Meditation
I
n a recent visit to the United States,
the Dalai Lama gave a speech at the
Society for Neuroscience’s annual
meeting in Washington, D.C. Over
the past several years, he has helped
recruit Tibetan Buddhist monks for—
and directly encouraged—research on
the brain and meditation in the Waisman
Laboratory for Brain Imaging and
Behavior at the University of WisconsinMadison. The findings from studies in this unusual sample, as well
as related research efforts, suggest
that over the course of meditating
for tens of thousands of hours, the
long-term practitioners had actually altered the structure and function of their brains.
In this article we discuss neuroplasticity, which encompasses such alterations,
and the findings from these studies.
Further, we comment on the associated
signal processing (SP) challenges, the
current status, and how SP can contribute to advancing these studies.
WHAT IS NEUROPLASTICITY?
The term neuroplasticity is used to
describe the brain changes that occur in
response to experience. There are many
different mechanisms of neuroplasticity,
ranging from the growth of new connections to the creation of new neurons.
When the framework of neuroplasticity
is applied to meditation, we suggest that
the mental training of meditation is fundamentally no different than other forms
of skill acquisition that can induce plastic changes in the brain [1], [2].
WHAT IS MEDITATION?
The term meditation refers to a broad
variety of practices, ranging from techDigital Object Identifier 10.1109/MSP.2007.910429
1053-5888/08/$25.00©2008IEEE
niques designed to promote relaxation to
exercises, performed with a more farreaching goal such as a heightened sense
of well-being. It is thus essential to be specific about the type of meditation practice
under investigation. In [3], meditation
was conceptualized as a family of complex
emotional and attentional regulatory
strategies developed for various ends,
including the cultivation of well-being
THE TERM NEUROPLASTICITY IS
USED TO DESCRIBE THE BRAIN
CHANGES THAT OCCUR IN
RESPONSE TO EXPERIENCE.
and emotional balance. Here we focus on
two common styles of meditation, i.e.,
focused attention (FA) meditation and
open monitoring (OM) meditation.
FA meditation entails voluntarily
focusing attention on a chosen object in a
sustained fashion. OM meditation involves
nonreactively monitoring the content of
experience from moment to moment, primarily as a means to recognize the nature
of emotional and cognitive patterns.
OM meditation initially involves the
use of FA training to calm the mind and
reduce distractions, but as FA advances,
the cultivation of the monitoring skill per
se becomes the main focus of practice. The
aim is to reach a state in which no explicit
focus on a specific object is retained;
instead, one remains only in the monitoring state, attentive moment by moment to
anything that occurs in experience.
These two common styles of meditation are often combined, whether in a
single session or over the course of a
practitioner’s training. These styles are
found with some variation in several
meditation systems, including the
IEEE SIGNAL PROCESSING MAGAZINE [176] SEPTEMBER 2007
Buddhist Vipassanā and Mahāmudrā,
and are also implicated in many popular
secular interventions that draw on
Buddhist practices.
FINDINGS OF BRAIN
CHANGES IN MEDITATION
In what follows, we summarize the
changes in the brain that occur during
each of these styles of meditation practice. Such changes include alterations in patterns of brain
function assessed with functional
magnetic resonance imaging
(fMRI), changes in the cortical
evoked response to visual stimuli
that reflect the impact of meditation on attention, and alterations
in amplitude and synchrony of highfrequency oscillations that probably
play an important role in connectivity
among widespread circuitry in the
brain.
EXPERIMENTAL SETUP
The experiments described below that
measure hemodynamic changes with
fMRI require a high-field-strength magnetic resonance imaging (MRI) scanner
equipped with the appropriate pulse
sequences to acquire data rapidly and
with the necessary fiber optic stimulus
delivery devices so that visual stimuli
can be presented to the subject while he
or she lays in the bore of the magnet.
For the studies that measure brain electrical activity, a high-density recording
system with between 64 and 256 electrodes on the scalp surface is used.
FA MEDITATION
A recent study [4] used fMRI to interrogate the neural correlates of FA
(continued on page 172)
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% T2 Accuracy: Times2 Versus 1
[in the SPOTLIGHT]
y=4
Novices
PZ
Time1
Amygdala
0.2
Blink
No-Blink
10
20
30
40
420-440 ms
0
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1,000 F-Values
−5μV
−200
0
−0.1
P3b to
T1
+5μV
Time2
r=−0.64
0.1
−0.2
Practitioners
ms
T1 T2
50
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r=−0.68,
p=.001
20
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(a)
Novices
Practitioners
40
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T1-Elicited P3b Amplitude: Time2 Versus 1
(b)
V
20
−20
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−20
(c)
F3
Fc5
Cp5
V2
500
300
100
0
F4
Fc6
Cp6
Blocks
50
100
Meditative State
Resting State
(d)
%
100
45
0
*
*
*
1 2 3 4 5 6 7 8 9 10
0
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Practitioners
*
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*
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Time (s)
(e)
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Controls
150
*
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Practitioners
0
Ongoing
Initial
Baseline Baseline
(f)
Meditation
State
(g)
[FIG1] Neuroimaging and neurodynamical correlates of FA and OM meditations. (a) Relationship between degree of meditation
training (in years) and hemodynamic response in the amygdala (in blue) to distractor sounds during FA meditation in long-term
Buddhist practitioners. Individual responses in the right amygdala are plotted (adapted from [4]). (b) The reduction in P3b amplitude (a
brain-potential index of resource allocation) to the first of two target stimuli (T1 and T2) presented in a rapid stream of distracter stimuli
after three months of intensive Vipassanā meditation [5]. (c) Generally, the greater the reduction in brain-resource allocation to T1 was
over time, the better able an individual became at accurately identifying T2 (adapted from [5] ). (d)–(e) Example of high-amplitude
gamma activity during a form of OM meditation, nonreferential compassion meditation, in long-term Buddhist practitioners [6]. (e)
Time course of gamma (25–42 Hz) activity power over the electrodes displayed in (d) during four blocks computed in a 20-s sliding
window every 2 s and then averaged over electrodes. (f) Intra-individual analysis of the ratio of gamma to slow oscillations (4–13 Hz)
averaged across all electrodes during compassion meditation. (g) The significant interaction between group (practitioner, control) and
state (initial baseline, ongoing baseline, and meditation state) for this ratio.
meditation in experts and novices.
The study compared FA meditation
on an external visual point to a rest
condition during which participants
do not use meditation and are simply
instructed to adopt a neutral baseline
state. The meditation condition was
associated with activation in multiple
brain regions implicated in monitoring (dorsolateral prefrontal cortex),
engaging attention (visual cortex),
and attentional orienting (e.g., the
IEEE SIGNAL PROCESSING MAGAZINE [172] JANUARY 2008
superior frontal sulcus, the supplementary motor area, and the intraparietal sulcus).
Although this meditation-related
activation pattern was generally stronger
for long-term practitioners compared to
novices, activity in many brain areas
involved in FA meditation showed an
inverted u-shaped curve for both classes
of subjects. Whereas expert meditators
with an average of 19,000 practice hours
showed stronger activation in these
areas than the novices, expert meditators with an average of 44,000 practice
hours showed less activation. This
inverted u-shaped function resembles
the learning curve associated with skill
acquisition in other domains of expertise, such as language acquisition. The
findings support the idea that, after
extensive FA meditation training, minimal effort is necessary to sustain attentional focus.
Expert meditators also showed less
activation than novices in the amygdala
during FA meditation in response to
emotional sounds. Activation in this
affective region correlated negatively
with hours of practice in life, as shown in
Figure 1(a). This finding may support the
idea that advanced levels of concentration are associated with a significant
decrease in emotionally reactive behaviors that are incompatible with stability
of concentration.
Collectively, these findings support
the view that attention is a trainable skill
that can be enhanced through the mental practice of FA meditation.
OM MEDITATION
Another study [5] recently examined
the idea that OM meditation decreases elaborative stimulus processing in
a longitudinal study using scalprecorded brain potentials and performance in an attentional blink task.
The consequence of decreased elaborative stimulus processing is that the
subject is able to better attend
moment-to-moment to the stream of
stimuli to which they are exposed and
less likely to “get stuck” on any one
stimulus.
The attentional blink phenomenon
illustrates that the information processing capacity of the brain is limited. More
specifically, when two targets T1 and T2,
embedded in a rapid stream of events,
are presented in close temporal proximity, the second target is often not seen.
This deficit is believed to result from
competition between the two targets for
limited attentional resources, i.e., when
many resources are devoted to T1 processing, too few may be available for
subsequent T2 processing.
The study in [5] found that three
months of intensive training in
Vipassanā meditation (a common style of
OM meditation) reduced brain-resource
allocation to the first target, as reflected
in a smaller T1-elicited P3b, a brainpotential index of resource allocation.
This is illustrated in Figure 1(b), which
shows the reduction in P3b amplitude.
In this figure, the scalp-recorded brain
potentials from electrode Pz, time-locked
to T1 onset as a function of T2 accuracy
[detected (no-blink) vesus not detected
(blink)], time (before or after three
months), and group (practitioners versus
novices) are shown. The scalp map shows
electrode sites where this three-way
interaction was significant between 420
and 440 ms.
The reduction in brain-resource
allocation to T1 was associated with a
smaller attentional blink to T2, as
shown in Figure 1(c). As participants
were not engaged in formal meditation
during task performance, these results
provide support for the idea that one
long-term effect of OM meditation may
be reduction in the propensity to “get
stuck” on a target as reflected in less
elaborate stimulus processing and the
development of efficient mechanisms
to engage and then disengage from
target stimuli in response to task
demands.
Previous studies [6] of high-amplitude pattern of gamma synchrony in
expert meditators during an emotional
version of OM meditation support the
idea that the state of OM may be best
understood in terms of a succession of
dynamic global states. Compared to a
group of novices, the adept practitioners self-induced higher amplitude sustained electroencephalography (EEG)
gamma-band oscillations and long-distance phase synchrony, in particular
over lateral fronto-parietal electrodes,
while meditating. Importantly, this pattern of gamma oscillations was also sig-
IEEE SIGNAL PROCESSING MAGAZINE [173] JANUARY 2008
nificantly more pronounced in the
baseline state of the long-term practitioners compared with controls, suggesting a transformation in the default
mode of the practitioners as shown in
Figure 1(g). Although the precise
mechanisms are not clear, such synchronizations of oscillatory neural discharges may play a crucial role in the
constitution of transient networks that
integrate distributed neural processes
into highly ordered cognitive and affective functions.
An example of high-amplitude gamma
activity during a form of OM meditation,
nonreferential compassion meditation, in
long-term Buddhist practitioners [6] is
shown in Figure 1(d) and (e).
The intra-individual analysis of the
ratio of gamma to slow oscillations (4–13
Hz) averaged across all electrodes during
compassion meditation is illustrated in
Figure 1(f). The abscissa represents the
subject numbers, the ordinate represents
the difference in the mean ratio between
the initial state and meditative state, and
the black and red stars indicate that this
increase is greater than two and three
times, respectively, the baseline standard
deviation.
The significant interaction between
group (practitioner, control) and state
(initial baseline, ongoing baseline, and
meditation state) for this ratio is shown
in Figure 1(g). The relative gamma
increase during meditation was higher
in the postmeditation session. In the initial baseline, the relative gamma was
already higher for the practitioners than
the controls and correlated with the
length of the long-term practitioners’
meditation training through life (adapted from [6]).
SP CHALLENGES
While SP has a unique opportunity to
contribute to this novel effort to
chart the manner in which the brain
may be transformed through the
mental practice of meditation, there
are several associated challenges.
Among these challenges are the characterization of different signatures of
brain function that distinguish
among different meditation practices,
[in the SPOTLIGHT]
continued
the parsing of variance in brain activity that may be due to changes in
peripheral physiology such as respiration, and the simultaneous measurement of electrical and hemodynamic
signals to harness the best temporal
and spatial resolution possible.
IMPACT ON BRAINCOMPUTER INTERFACES
One of the interesting implications of
the research on meditation and brain
function is that meditation might help
to reduce “neural noise” and so enhance
signal-to-noise ratios in certain types of
I N D I A N A U N I V E R S I T Y • P U R D U E U N I V E R S I T Y • F O R T WAY N E
FOUNDING DIRECTOR OF THE
CENTER OF EXCELLENCE IN WIRELESS
COMMUNICATION RESEARCH
Indiana University-Purdue University Fort Wayne (IPFW) Department of Engineering invites applications and
nominations for the position of Founding Director of the Center of Excellence in Wireless Communication Research.
Candidates must possess a recognized national reputation for research excellence in the field of wireless
communication. Master’s degree required; possession of an earned doctorate in electrical engineering or its
equivalent is highly desired. Preference will be given to candidates with a strong history of applied research, industry
collaboration, and experience in Department of Defense-funded projects.The initial appointment will be for a period
of three years with the option for subsequent renewal based upon performance.
IPFW is a regional campus of both Indiana University and Purdue University and is the largest university in northeast
Indiana. Serving more than 12,000 students and offering more than 180 degree options, IPFW is a comprehensive
university with a strong tradition of service to and collaboration with the region.
The Department of Engineering offers B.S. degrees in electrical, computer, civil, and mechanical engineering.The M.S.
degree in engineering with concentrations in electrical, mechanical, computer, and systems engineering will be
launched during the 2007-2008 school year. The department presently includes 16 full-time faculty members and
has approximately 300 undergraduate students.
tasks. In contexts where brain-computer interfaces are being developed that
are based upon electrical recordings of
brain function, training in meditation
may facilitate more rapid learning. This
idea warrants systematic evaluation in
the future.
FUTURE WORK
Ongoing and future work focuses on a
few distinct directions. One of the crucial
areas requiring attention is the characterization of changes in connectivity
among the various brain circuits that are
engaged by these practices. The development of new methods to probe different
aspects of connectivity (both structural
and functional) will be extremely valuable in furthering this line of inquiry.
The goal of such work is to better understand how different circuits are integrated during meditation to produce the
behavioral and mental changes that are
said to occur as a result of such practices, including the promotion of
increased well-being.
•
Establish a wireless laboratory to support courses in wireless communication.
•
Develop a series of undergraduate courses that would lead to an undergraduate certificate in wireless
communication.
AUTHORS
Richard J. Davidson (rjdavids@wisc.
edu) is a director and Antoine Lutz
(alutz@wisc.edu) is an associate scientist,
both with the Waisman Laboratory for
Brain Imaging and Behavior, University
of Wisconsin-Madison.
•
Develop and teach courses for the Master of Science in Engineering (MSE) – electrical engineering
concentration – that would lead to a graduate certificate in wireless communication.
REFERENCES
•
Develop and offer credit and non-credit professional development experiences for regional employees.
The Founding Director of the Center of Excellence in Wireless Communication Research shall have the following
responsibilities:
•
Establish the Center of Excellence in Wireless Communication Research, emphasizing the practical application
of wireless technology for the needs of the regional defense industry.
•
Expand collaboration with industry through sponsored research.
•
Participate in IEEE 802.X standards development.
•
Coordinate and host conferences on the application of wireless technology with an emphasis on defense
applications and emerging commercial wireless technologies.
This position offers a unique opportunity to build a Center of Excellence in Wireless Communication Research and
to significantly expand industry-university collaborative research in the fields of wireless networks.
IPFW offers a competitive salary and benefits package and an excellent work environment. Fort Wayne is the second
largest city in Indiana and is located within several hours of Chicago, Columbus, Cincinnati, Detroit, and Indianapolis.
It boasts affordable housing, a low cost of living and a safe environment in which to raise a family.The region is home
to seven major defense contractors employing over 1,800 engineers working in the fields of wireless communication,
sensor networks, C4, network-centric systems, and defense products.
Applicants with extensive industrial rather than university career experience will be given serious consideration and
are strongly encouraged to apply. Candidates demonstrating extensive contact networks within the business and
governmental sectors will be preferred.
To apply for this position, please visit our Web site at www.ipfw.jobs. Applicants should submit a cover letter
addressing wireless communication and DoD knowledge and experience, resume/vita, statement of research and
teaching experience, and the names and contact information for at least three references.
The committee will begin review of applications immediately and the search will remain open until the position is
filled. For additional information regarding IPFW and the Department of Engineering please visit the Web sites at:
www.engr.ipfw.edu and www.ipfw.edu.
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IEEE SIGNAL PROCESSING MAGAZINE [174] JANUARY 2008
[1] A. Berger, O. Kofman, U. Livneh, and A. Henik,
“Multidisciplinary perspectives on attention and the
development of self-regulation,” Prog. Neurobiol.,
vol. 82, no. 5, pp. 256–286, 2007.
[2] R.A. Poldrack, “Neural systems for perceptual
skill learning,” Behav. Cognit. Neurosc. Rev., vol. 1,
no. 1, pp. 76–83, 2002.
[3] A. Lutz, J.P. Dunne, and R.J. Davidson,
“Meditation and the neuroscience of consciousness:
An introduction,” in The Cambridge Handbook of
Consciousness, P.D. Zelazo and E. Thompson, Eds.
Cambridge, U.K.: Cambridge Univ. Press, in press.
[4] J.A. Brefczynski-Lewis, A. Lutz, H.S. Schaefer,
D.B. Levinson, and R.J. Davidson, “Neural correlates
of attentional expertise in long-term meditation
practitioners,” Proc. Nat. Acad. Sci., vol. 104, no. 27,
pp. 11483–11488.
[5] H.A. Slagter, A. Lutz, L.L. Greischar, A.D. Francis,
S. Nieuwenhuis, J.M. Davis, and R.J. Davidson,
“Mental training affects use of limited brain
resources,” PLoS Biol., vol. 5, no. 6, pp. e13800010008, 2007.
[6] A. Lutz, L. Greischar, N.B. Rawlings, M. Ricard,
and R.J. Davidson, “Long-term meditators self-induce
high-amplitude synchrony during mental practice,”
Proc. Nat. Acad. Sci., vol. 101, no. 46, pp.
16369–16373, 2004.
[SP]